Fluid fuel burner control system

ABSTRACT

Fluid fuel burner control system utilizing solid state components, and in which the several components, with their interconnecting circuitry, can be compactly mounted upon a panel or in a box, and installed in any desired location with a limited number of terminals for accommodating single conductors leading to the respective legs of an alternating current source of electrical energy, the fuel valve, an igniter and a flame sensor, which may be located remotely from the compact control panel or close to it, as desired. The circuitry of the system places the operation of the fuel valve under the control of an igniter circuit transformer and places the energization of the igniter circuit transformer under the control of a flame sensor, while the usual safety switch is responsive only to current which traverses the primary of the transformer which energizes the igniter, and the interruption of current flow through the transformer depends upon the electrical conductivity of flame at the burner.

United States Patent Conner [54] FLUID FUEL BURNER CONTROL SYSTEM [72]Inventor: Leonard E. Conner, St. Louis, Mo.

[73] Assignee: Eaton Yale & Towne Inc., Cleveland, Ohio [22 Filed: Nov.13, 1969 [21] App]. No.: 876,472

[52] US. Cl ..43l/78, 431/254 [51] Int. Cl ..F23n 5/00 [58] Field ofSearch ..43 1/6, 24, 66, 70, 78, 254

[56] References Cited UNITED STATES PATENTS 3,445,172 5/1969 Zielinski..3 H78 X 3,446,565 5/1969 l-lantack ....431/70 3,520,645 7/1970 Cottonet al.. ....431/78 3,510,236 5/1970 Potts ...431/66 X PrimaryExaminer-Edward G. Favors Attorney-Teagno and Toddy ABSTRACT Fluid fuelburner control system utilizing solid state components, and in which theseveral components, with their interconnecting circuitry, can becompactly mounted upon a panel or in a box, and installed in any desiredlocation with a limited number of terminals for accommodating singleconductors leading to the respective legs of an alternating currentsource of electrical energy, the fuel valve, an igniter and a flamesensor, which may be located remotely from the compact control panel orclose to it, as desired. The circuitry of the system places theoperation of the fuel valve under the control of an igniter circuittransformer and places the energization of the igniter circuittransformer under the control of a flame sensor, while the usual safetyswitch is responsive only to current which traverses the primary of thetransformer which energizes the igniter, and the interruption of currentflow through the transformer depends upon the electrical conductivity offlame at the burner.

5 Claims, 1 Drawing Figure FLUID FUEL BURNER CONTROL SYSTEM Theinvention relates generally to the control of fluid fuel burners, suchas those provided in domestic appliances, heating systems and the like,and is an improvement upon the system disclosed in US. Pat. No.3,446,565.

Systems of the character referred to are usually provided with one orboth of a manually adjustable timer switch and temperature switch," aswell as a safety switch. Such switches usually take the form of abimetallic or other thermostat connected in series with the source ofelectrical energy. In the case of the safety switch, a length of heaterwire, or other electrical resistance adapted to generate heat, isusually provided adjacent the bimetallic element, so as to provide finecontrol over the time period during which the safety switch can remainin closed circuit position while the fuel valve is open, but withoutbeing ignited. In a typical situation, as illustrated in the aforesaidpatent, the heater element of the safety switch is energized at fullline voltage-with normally functioning ignition-until a heat-sensingswitch adjacent the burner has been sufficiently heated to move from itsnormally closed position to the open position. Thus, whether or notthere is a fault in the igniter circuit, the heater element of thesafety switch must be energized at least for a period not onlysufficient normally to ignite a flame at the burner, but for a periodthereafter sufficient-with normally functioning ignitionfor that flameto have produced heat enough to actuate the burner-heat-sensingswitch-before the safety switch can interrupt the circuit which iskeeping the fuel valve open.

One object of the invention is to provide a control system for a fluidfuel fired device having an electrical igniter, and in which the fuelvalve cannot open until the igniter circuit is energized, and cannotlong remain open in the absence of flame at the burner.

Another object is to provide a compact prewired panel or box mountingthe necessary control devices and circuitry for automatic control of afluid fuel burning device, and which can be installed as a unit at anychosen location and connected to the device, near or far, in a simpleand fool prooffashion.

A further object is to provide such a system in which the severalcontrol operations are accomplished without radio interference, or otherdisquieting noises.

These and other objects of the invention are achieved by the use ofstatic control components; making the opening of the fuel valve todepend upon the fact of current flow through the primary of an ignitiontransformer; making the opening of the usual safety switch to dependsolely upon the duration and magnitude of current supplied to theprimary of the ignition transformer; and making the flow of currentthrough the primary of the ignition transformer to depend upon thenon-existence of (as distinguished from the heat developed by existing)flame at the burner, which is to say that the electrical conductivity offlame is utilized to deactivate the ignition system, as well as toautomatically reactivate the ignition system if the burner flame isblown out or is otherwise unintentionally extinguished without having toawait the cooling-off period required by the usual heat-responsiveswitch at the burner.

One embodiment of the invention is diagrammatically illustrated in theaccompanying drawing, which is a circuit diagram associated withdiagrammatically represented appurtenances including a fluid fuel valve,its supply line, a burner, an igniter, and a flame sensor. In theaccompanying drawing, the broken line M delineates the margins of amounting panel or box which supports the various electrical controldevices (except those which, for convenience, are preferably locatedremotely) and the interconnecting circuitry in the form util ized in oneembodiment of the invention. In the form shown, the mounting panel M isprovided with six binding posts T-l, T-Z, T-3, T4, T-S and T-6, whichprovide terminals for the circuitry mounted on mounting panel M, and ateach of which a single electrical conductor, extending respectively toremote instrumentalities, may be readily connected. In the embodimentshown, the control system is intended to be energized by an alternatingcurrent source, such as a conventional 120 volt, 60 cycle domesticservice, the opposite legs of which are designated L-l and L-2 in thedrawing, which connect respectively with binding posts T-] and T-2 ofthe mounting panel M. Of course, if the supply has one leg grounded, itwill be understood that terminal T-2 can be grounded.

As illustrated, line L-l is provided with a conventional seriesconnected timer switch TM and a conventional temperature switch TR,which may be, and frequently are, located remotely from the mountingpanel M.

Binding post T-3 is intended to be electrically connected with a flamesensor SS having an electrically conductive probe P which extends into aposition to be enveloped by, or at least in contact with, any flameproduced at burner B. Burner B is served with fluid fuel, such as gas,supplied through a conduit controlled by valve V, which may be anysuitable electromagnetically operated valve having an inductiveoperator, such as solenoid S, the opposite terminals of which areconnected to binding posts T-S and T-6. The valve V and the burner Bmay, or course, be located remotely from the panel M, as desired.

Binding post T-4 serves to connect a lead serving an igniter I having aspark gap located at the burner in a position such as to be adjacent, orenveloped by, the stream of fuel emerging from the burner when the valveV is in open position.

From binding post T4, line L-l extends to a junction 14, where it isdivided into three branches, one extending through a resistance heater H(which forms a part of the conventional safety switch) and thence todiode D4. Another branch extends to diode D-2. The third branch extendsfrom junction J- l to the switching element S-F of the aforesaidconventional safety switch, and from thence to diode D3. The diodes D-l,D-2 and D-3 are biased to pass current only in the direction indicatedby their arrow-heads. By virtue of the presence of the diodes in thethree circuit branches extending from junction 1- 1, it will beunderstood that the electrical energy supplied to the several componentswithin, and served by, the instrumentalities mounted upon the mountingpanel M is a half-waverectified alternating current, sometimes referredto as a pulsating current."

From diode D-l, the pulsating current is supplied to one end of theprimary of transformer TF, as well as to one side of capacitor C-l, theother side of which is directly connected with binding post T-2, andfrom thence to line L-Z, which is the opposite leg of the alternatingcurrent source of which line L-l is a part. Thus, the primary oftransformer TF and capacitor C-l receive charges of voltage, throughdiode D1, during the on-half-cycles at which L-l is positive to L-Z; andafter about nine such on-half-cycles, the capacitor C-] will have becomecharged to line voltage and will begin to discharge into the primary oftransformer TF during the off-half-cycles at which L-] is negative toL-2, but the direction in which the capacitors discharge is impressedupon the transformer is the same as that impressed through D-l duringthe on-half cycles. One end of said secondary being grounded asindicated by the forked symbol whose counterpart appears at the centerof burner B, the induced voltage is transmitted through terminal T-4 tothe spark gap at igniter I so that the igniter circuit is alive beforeany current actually flows through the primary of the transformer.

Flow of current through the primary of transformer TF is controlled by asilicon-controlled rectifier SCR-2, which, when triggered, permits thepulsating current to flow through the primary of transformer TF towardjunction .l-2, through resistor R-3, and thence through terminal T-2 toline L-Z, thereby increasing the voltage induced in the secondary TFS ofthe transformer to a value sufficient to throw an arc across the sparkgap of igniter I.

To trigger SCR-2, and thus permit the flow current therethrough towardL-2, a capacitor C-2 is charged via diode D-2 and resistor R-l throughjunction 1-3. The opposite side of condenser C-2 is connected directlyto terminal T-2, as shown. After a number of half-cycles in which L-l ispositive to L4, the capacitor C-2 will become charged to the breakovervoltage of neon tube N (which, as shown, is connected through junction1-3 to capacitor C-2) whereupon a triggering signal will be transmittedto the cathode of SCR-2, and cause it to become conductive in thedirection toward .14.

Once SCR-2 is fired from condenser C-2, condenser C-] will dischargethrough the primary of the transformer. This is a pulse discharge, butwhen the magnetic field of the transformer primary collapses, it inducesan EMF opposite that which existed by virtue of the discharge ofcondenser C-l thereby tending to recharge C-l. This creates aninstantaneous reversal of current through SCR-2, which, once its currenthas passed through the zero value, the SCR is restored to blocking stateand has to be retired to become conductive in the direction from L-!toward L-2.

The values of the resistance R-l, condenser C-2 and neon tube N-l arechosen so that SCR-2 will be reflred six times per second, but oncethere is flame at sensor P, the condenser C-2 will be short-circuitedthrough J-3, R-2 and D-S to T-2, so that there is no longer the storagecapacity at C-2 to retire SCR-2.

However, before there can be flame at sensor P, valve V must be openedto supply fuel to burner B. The series circuit from 1-1 through thenormally closed safety switch S-F, diode D-3, terminal T-S, and solenoidS, is live at all times except when one or more of switches TM, TR andS-F is open, but no current can traverse the solenoid until SCR-l istriggered into a state of conductivity toward T-2, and, according to theinvention, a condition precedent to such triggering of SCR-1 is thatcurrent be flowing through the primary of transformer TF and throughSCR-2 toward R-3 and 1-4.

Current flowing through the primary of transformer TF and SCR-2 dividesat junction J-Z, part passing through resistor R- 3, and another partpassing through resistor R-6 to the cathode of SCR-1, and it is thelatter which triggers SCR-l into a state of conductivity toward terminalT-2 and junction J-4. Resistor R-3 is designed to create, whenenergized, a voltage difference on the order of to volts between itsopposite ends, and thereby becomes an ancillary source of electromotiveforce tending to drive current from junction 1-2 through R-6, to thecathode of SCR-1, and back toward R-3 through junction 1-4, therebyrendering SCR-l conductive, and thus initiating the energizationofsolenoid S to open valve V and admit fuel to the burner B, wheresparking is already occurring at l.

During the time SCR-2 remained in a current blocking state, no currentcould flow from junction J-3 through resistor R-2 and diode D-S toterminal T-3 because no flame was existing at the burner B through whichan electrical charge from probe P could be grounded or otherwisecomplete its circuit back to L-2. However, once flame has occurred atburner B, the electrical conductivity of that flame is utilized toground probe P and its conductively connected components (diode D-5 andresistor R-Z) back to junction 1-3. This permits capacitor C-Z todischarge through the last-mentioned components and so reduces thevoltage on neon tube N that it cannot transmit a triggering signal tothe gate of SCR-2, while flame is bridging the gap between probe P andgrounded burner B.

lf, despite the'sparking at l, ignition fails to occur, the heater Hwill, within a safe period of time, have actuated the safety switch SFinto open circuit position, thereby effecting closure of valve V.Assuming, however, that ignition does occur before sufficient time haselapsed for heater H to actuate switch SF into its open circuitposition, the valve V remains open as long as it is energized by currentflowing through solenoid S. By virtue of the presence of diode D-3 inthe circuit, the current which energized solenoid S is also a pulsatingone which, during its on-half-cycle, also charges capacitor C-3, whichin turn, during the off-half-cycle of the current flowing through D-3discharges through solenoid S in the same direction as the currentdelivered in the on-half-cycle through D-3, thereby locking in thesolenoid. in order to assure that SCR-l does not, at any time, resumeits current-blocking state, a loop circuit, including diode D4 (biasedto pass current toward terminal T-S), is provided to accommodate thecurrent induced within the solenoid S by the collapsing flux whichintervenes the peaks of successive half-cycles.

During the period preceding actual ignition of fuel at the burner B, theelements between 1-3 and probe P of the sensor have been charged, but nocurrent has been able to flow therethrough because there was nothing toconduct electrical current from probe P to the grounded burner B. Onceflame occurs, however, the conductivity of the flame is utilized toconduct current from probe P to the grounded burner, thereby completinga circuit which prevents further charging of capacitor C-2, and furtherdischarging thereof through neon tube N to trigger SCR-2. At this time,SCR Z will suffer a reversal of current direction at the end of the nexton-half-cycle. Such reversal of current causes the flow through SCR-2 topass through zero which restores SCR-2 to its blocking state, unless anduntil it is triggered again, but since the triggering instrumentalitiesare now grounded through .l-3, R-2, D-5 and sensor SS through flame toburner B, SCR-2 cannot be retriggered as long as flame persists at theburner.

For optimum performance on 115 volt, 60 cycle alternatingcurrent-source, it is preferred that the several components of theembodiment illustrated in the drawing have the following magnitudes andcharacteristics:

Heater H: 1,000 ohms Diodes: l ampere, 200 volt Transformer: l0 kv,output pulse transformer Resistor R-I: 5.0 megohms Resistor R-21 0.]megohms Resistor R-J: 0.47 ohms Resistor R-4: 0.75 megohms Resistor R5:0.75 megohms Resistor 11-6: 5 l0 ohms Capacitor C- l: 20 micro-faradsCapacitor (-21 0.22 micro-farads Capacitor C-3: 2.0 microfaruds SolenoidS: 500 ohms (DC); 2,000 ohms impedance at 60 eyc.

Neon Bulb N: Brealtover voltage Maintaining voltage 60 SCR's: 7 ampere,300 volt Flame: 8 megohrns between probe and burner From the foregoingdescription, those skilled in the art will understand that under normaloperating conditions, the system provides a sequence of operations whichmay be subdivided into several steps as follows:

With current available, a high voltage pulse spark occurs and is provenbefore the automatic main burner gas valve becomes energized.

Proof of spark signals the automatic gas valve circuit to be energized,

A safety lockout circuit turns off the gas valve circuit within apredetermined time interval if no proof of flame exists.

If flame is present, the sensor probe circuit responds to deenergizeboth the igniter circuit and the safety lockout circuits.

if current interruption occurs by means of a switch, thermostat switchor power loss, the gas valve circuit is deenergized and remains offuntil the current returns and a normal ignition cycle ensues.

Under abnormal conditions, the system reacts as follows:

If spark gap at l is shorted, excessive current will flow through heaterH and switch SF will open within seconds to deenergize the gas valvecircuit.

If the sensor SS is shorted from a cold start, the gas valve circuitremains deenergized because SCR-1 cannot be triggered.

if, for some reason, the gas valve is energized, and gas is beingdischarged at the burner without ignition, the heater H will, within ashort time interval, actuate switch SF to close the valve, but theigniter circuit remains on and only turns off through actuation of aconventional timer such as TM.

A particular advantage of the system disclosed is that the prewiredpanel M operates to accomplish the same results regardless of polarityof lines L-l and L-2, and regardless of which, if either, of the sourcelegs is grounded. For example, when line L-2 is grounded at the powersource, the flame senlOlOTI sor circuit extends from junction 1-3through resistor R-2, diode Du5, sensor probe P (which may be astainless steel bar) through the flame to the burner which is grounded.On the other hand, ifline L-Z is not grounded at the power source, theflame sensing circuit extends from junction 1-3 through R-Z, D-2, thesensor probe and the flame to the grounded burner as before, but fromthe grounded burner, the circuit is completed through ground to theground (forked symbol) at the lower end of transformer secondary TFS,and from there through resistors R-5 and R-4 and terminal T-2 to lineL-2. The third alternative is that L-l be grounded at the supply source,in which case an infinitive impedance will exist between terminal T-3and terminal T-l during the half-cycle of the supply source when L1 ispositive with reference to L-2, the flame sensor circuit will be madefrom 1-3 through R-2, D-S, T-3, probe P and flame to ground at burner B.Hence, the prewired panel M can be installed without regard to which, ifeither, leg of the supply source is grounded. It is, however, sometimesdesirable to provide the burner with two grounds, one always being apart of the igniter circuit and having its counterpart at the lower endof transformer secondary TFS, and the other serving optionally tocomplete the flame sensor circuit when L-2 is grounded.

While one complete embodiment of the invention has been disclosed indetail, the invention is not limited to the details of that embodiment.

What is claimed is:

l. A fluid fuel burner control system comprising a burner, anelectromechanical valve for controlling the flow of fuel to said burner,said valve having a deenergized condition preventing the flow of fuel tosaid burner and an energized condition providing for the flow of fuel tosaid burner, an igniter for igniting fuel flowing from said burner, aflame sensor for sensing the presence of a flame at said burner, firstcircuit means for activating said igniter, second circuit means having afirst nonconductive condition in which said valve is deenergized and asecond conductive condition for energizing said valve to enable fluid toflow to said burner, and third circuit means connected to said flamesensor for rendering said first circuit means ineffective to activatesaid igniter by establishing a ground potential between said firstcircuit means and said flame sensor when said flame sensor senses thepresence of a flame at said burner, said first circuit means beingconnected to said second circuit means for biasing said second circuitmeans to said second conductive condition to energize said valve inresponse to the flow of current through said first circuit means whichefi'ects activation of said igniter by said current flow in said firstcircuit means.

2. A fluid fuel burner control as defined in claim 1 wherein said secondcircuit means includes a first SCR having a conductive condition forenergizing said valve and a nonconductive condition for deenergizingsaid valve, said first SCR including a gate connected to said firstcircuit means for rendering said first SCR conductive upon theapplication ofa positive gating potential thereto by said first circuitmeans to effect energization of said valve, said first circuit meanseffecting the application of said positive gating potential to said gateof said first SCR in response to activation of said igniter by saidfirst circuit means.

3. A fluid fuel control as defined in claim 2 wherein said first circuitmeans includes a transformer having a primary winding and a secondarywinding, a second SCR having a conductive and a nonconductive conditionfor controlling the energization of said primary winding of saidtransformer, said second winding of said transformer being connected tosaid igniter and having a current induced therein when said primarywinding is energized and said second SCR is conductive, said second SCRincluding a cathode connected to said gate of said first SCR to providesaid positive gating potential thereto upon conducting of said secondSCR, energization of said primary winding and activation of said igniterby current induced in said secondary winding.

4. A fluid fuel control as defined in claim 3 wherein said first circuitmeans further includes a capacitor for effecting the application of apositive gating potential to the gate of said second SCR and whereinsaid third circuit means is connected to said capacitor and preventssaid capacitor from charging to apply said positive gating potential tosaid gate of said second SCR when said flame sensor senses the presenceof a flame at said burner.

5. A fluid fuel control as defined in claim 4 further including a safetyswitch having a heating element and a switching element movable from anormally conductive condition to a nonconductive condition in responseto said heating element reaching a predetermined temperature for apredetermined amount of time, said heating element being seriesconnected with said primary winding of said transformer and beingenergized when said primary winding is energized to effect actuation ofsaid igniter, said switching element being series connected with saidfirst SCR for rendering said first SCR nonconductive when said switchingelement moves to said nonconductive condition to deenergize said valve.

1. A fluid fuel burner control system comprising a burner, anelectromechanical valve for controlling the flow of fuel to said burner,said valve having a deenergized condition preventing the flow of fuel tosaid burner and an energized condition providing for the flow of fuel tosaid burner, an igniter for igniting fuel flowing from said burner, aflame sensor for sensing the presence of a flame at said burner, firstcircuit means for activating said igniter, second circuit means having afirst nonconductive condition in which said valve is deenergized and asecond conductive condition for energizing said valve to enable fluid toflow to said burner, and third circuit means connected to said flamesensor for rendering said first circuit means ineffective to activatesaid igniter by establishing a ground potential between said firstcircuit means and said flame sensor when said flame sensor senses thepresence of a flame at said burner, said first circuit means beingconnected to said second circuit means for biasing said second circuitmeans to said second conductive condition to energize said valve inresponse to the flow of current through said first circuit means whicheffects activation of said igniter by said current flow in said firstcircuit means.
 2. A fluid fuel burner control as defined in claim 1wherein said second circuit means includes a first SCR having aconductive condition for energizing said valve and a nonconductivecondition for deenergizing said valve, said first SCR including a gateconnected to said first circuit means for rendering said first SCRconductive upon the application of a positive gating potential theretoby said first circuit means to effect energization of said valve, saidfirst circuit means effecting the application of said positive gatingpotential to said gate of said first SCR in response to activation ofsaid igniter by said first circuit means.
 3. A fluid fuel control asdefined in claim 2 wherein said first circuit means includes atransformer having a primary winding and a secondary winding, a secondSCR having a conductive and a nonconductive condition for controllingthe energization of said primary winding of said transformer, saidsecond winding of said transformer being connected to said igniter andhaving a current induced therein when said primary winding is energizedand said second SCR is conductive, said second SCR including a cathodeconnected to said gate of said first SCR to provide said positive gatingpotential thereto upon conducting of said second SCR, energization ofsaid primary winding and activation of said igniter by current inducedin said secondary winding.
 4. A fluid fuel control as defined in claim 3wherein said first circuit means further includes a capacitor foreffecting the application of a positive gating potential to the gate ofsaid second SCR and wherein said third circuit means is connected tosaid capacitor and prevents said capacitor from charging to apply saidpositive gating potential to said gate of said second SCR when saidflame sensor senses the presence of a flame at said burner.
 5. A fluidfuel control as defined in claim 4 further including a safety switchhaving a heating element and a switching element movable from a normallyconductive condition to a nonconductive condition in response to saidheating element reaching a predetermined temperature for a predeterminedamount of time, said heating Element being series connected with saidprimary winding of said transformer and being energized when saidprimary winding is energized to effect actuation of said igniter, saidswitching element being series connected with said first SCR forrendering said first SCR nonconductive when said switching element movesto said nonconductive condition to deenergize said valve.